#include <cstdio>
#include <fstream>
#include<math.h>
int n,i,poz,nr;
bool v[2000010];
using namespace std;
int main()
{
	ifstream f("ciur.in");
	ofstream g("ciur.out");
	f >> n;
	poz = 2;
	while (poz != n)
	{
		for (i = poz+poz;i <= n - 1;i = i + poz)
			v[i] = 1;
		poz++;
		while (v[poz] == 1)
			poz++;

	}
	for (i = 2;i <= n - 1;i++)
		if (v[i] == 0)
			nr++;
	g << nr;


	return 0;
}